Light olefins such as ethylene, propylene, butylene and mixtures thereof, serve as feeds for the production of numerous important chemicals and polymers. A common method for producing light olefins is by cracking of petroleum feeds. However, because of the limited supply of competitive petroleum feeds, the opportunities to produce low-cost light olefins from petroleum feeds are limited. Efforts to develop light olefin production technologies based on alternative feeds have increased. For example, oxygenates such as alcohols, in particular methanol and ethanol, dimethyl ether, methyl ethyl ether, dimethyl carbonate and methyl formate are being considered as alternative feeds for the production of light olefins. These oxygenates-to-olefins processes typically use molecular sieve catalysts to promote the conversion of oxygenates to olefins. However, it has been found that during this reaction, carbonaceous material such as coke is deposited on or within the molecular sieve catalysts. Over-accumulation of this coke interferes with the catalyst's ability to promote the oxygenates-to-olefins reaction. Accordingly, the oxygenates-to-olefins process typically includes a step for regenerating the catalyst, which at least partially removes the coke from the catalyst by combustion in the presence of oxygen. The regenerated catalyst may then be reused in the oxygenates-to-olefins reaction.
It has been found that as a result of this regeneration step, oxygen molecules become entrained within the pores of the catalyst or interstitially between the catalyst particles themselves. It has also been found that over-abundance of these oxygen molecules reduce the activity and selectivity of the molecular sieve during the oxygenates-to-olefins reaction. It is therefore desirable to reduce the amount of entrained oxygen molecules present in regenerated catalyst prior to introduction of the regenerated catalyst into the oxygenates-to-olefins reactor. This invention satisfies this need.